Cyrus, along with other celebrities, are a symptom of what happens to people, when they are never told 'no' (there was even an interview with Billy Ray Cyrus, when he said he'd wants to be known as Miley's 'friend' rather than 'disciplinarian', from a few years back).
Anyway, never being told 'no', along with few, if any consequences of bad actions, along with the general idea in places like Hollywood, that you should be able to do anything you want, leads to this sort of thing.
If you notice, celebrities like Ron Howard, who wind up being a decent person, is a rarity, especially among child stars. Ron credits much of that, to Andy Griffith keeping him pointed in the right direction when he was younger.
